1. Field of the Invention
The present invention relates to an ink jet recording head for ejecting ink to a recording surface of a recording medium to obtain a recorded image thereon.
2. Related Background Art
There are practically available ink jet recording devices for selectively ejecting ink from a plurality of ink ejection outlets onto the recording surface of recording medium, based on recording data, thereby depositing the ink on the recording surface to form an image. Such ink jet recording devices have an ink jet recording head selectively mounted on a carriage portion, which is disposed opposite to the recording surface of recording medium and which is arranged to undergo scanning in directions perpendicular to the conveying direction of the recording medium.
The ink jet recording head of a side shooter type is comprised, for example as shown in FIG. 25, of main body section 2 consisting of ink supply section 2B, to which ink tank IT is mounted, and input terminal section 2A electrically connected to the carriage portion not illustrated and receiving a drive control signal group from the carriage portion; recording element board 6 joined to a joined surface in the ink supply section 2B of the main body section 2; and printed wiring board 4 electrically connected to the recording element board 6 and supplying the drive control signal group from the input terminal section 2A thereto.
The ink supply section 2B in the main body section 2 is formed, for example, in such a manner that block piece 8 made of an aluminum alloy is integrally molded in a resin, as shown in FIG. 26A. The ink supply section 2B is provided with ink supply passage 2a for guiding the ink from the ink tank IT thereinto. One opening end of the ink supply passage 2a is open in the joined surface 2b including a portion exposed to the outside in the block piece 8.
The recording element board 6 is comprised, as shown in FIG. 26B and FIG. 29, of substrate 10 having ink supply opening portion 10c in communication with the opening end of the ink supply passage 2a in the ink supply section 2B, partition member 12 for forming a plurality of ink branching supply passages 12a provided respectively corresponding to heaters 10a as ink heating portions in the substrate 10, and orifice plate 14 in which a plurality of ink ejection outlets 14a are arrayed in two parallel strings and opposite to the respective heaters 10a in the substrate 10.
The substrate 10 in the recording element board 6 is made of, for example, a silicon material of the thickness of 0.5 to 1.0 mm. Provided in the surface of the substrate 10 bonded to the joined surface 2b of the ink supply section 2B with an adhesive is ink supply opening portion 10c extending in the array direction of the ink ejection outlets 14a and opposite to the orifice plate 14, as shown in FIG. 27A and FIG. 26B.
Further, the heaters 10a are arranged at predetermined mutual intervals on either side of the ink supply opening portion 10c in the substrate 10. One ends of the ink branching supply passages 12a in the partition member 12 are in communication with the ink supply opening portion 10c and each ink branching supply passage 12a is arranged to guide the ink supplied through the ink supply opening portion 10c to the associated heater 10a.
The printed wiring board 4 is electrically connected to each electrode 10b of the substrate 10 in the recording element board 6, as shown in FIG. 29. The printed wiring board 4 has recording element board receiving section 4B in which the recording element board 6 is placed, and terminal section 4A disposed in the input terminal section 2A in the main body section 2.
In this arrangement, when a drive control signal is supplied to each heater 10a of the substrate 10 in the recording element board 6 through the printed wiring board 4 to heat the heater 10a, the ink introduced through the ink branching supply passages 12a is heated, bubbles are generated therein by the film boiling phenomenon, and with expansion of the bubbles thus generated, the ink is ejected from the ink ejection outlets 14a toward the recording surface of recording medium.
In the arrangement wherein the recording element board 6 in the printed wiring board 4 fixed to the main body section 2 is bonded to the joined surface 2b in the main body section 2 with the adhesive as described above, when the recording element board 6 is excited into the recording operation state as described above, the temperature of the block piece 8 in the joined surface 2b in the main body section 2 increases as the temperature of the recording element board 6 increases. This causes the recording element board 6 and block piece 8 to thermally expand. However, since there is a difference between an expansion coefficient of the recording element board 6 made of silicon and an expansion coefficient of the block piece made of the aluminum alloy, there would occur some cases wherein the recording element board 6 is deformed so that the arrays of ink ejection outlets near the central portion are so curved as to approach each other as deviating from the straight line as shown in FIG. 28, or cases wherein the recording element board 6 is broken. Especially, when a thermosetting adhesive is used, it might be deformed or broken.
In such cases, it is also conceivable to increase the thickness or the surface area in order to enhance the rigidity of the recording element board 6, but it is not wise, because it also increases the manufacturing cost of the recording element board 6.